Electric transformer-furnace.



O FRIGK.

ELECTRIC TRANSFORMER FURNACE,

APPLICATION FILED $13114, 1906. RENEWED MAR. 20, 1903.

- Zn mania,

o'rTo ERICK, F sALTsJ'ciBADEN, swEDEN, ASSIGNOR TO THE GRfiNDAL KJ'ELLIN COM- UNITE STATES PATENT OFFICE.

PANY, LIMITED, o- LONDON, ENGLAND.

ELECTRIC TRANSFORMER-FURNACE.

Specification of Letters Patent.

Patented Sept. "7, 1909.

Application filed September 14, 1906, Serial No. 334,648. Renewed March 20, 1908. Serial No. 422,236.

To all whom it may concern:

Be it known that I, OTTO Fnioit, a subject of the King of Sweden, and resident of Saltsjtibaden, Sweden, have invented new and useful Improvements in Electric Trans- ,former-l urnaccs, of which the following is a specification, reference being had to the drawing accompanying and forming a part hereof. This invention relates to electric transformer furnaces.

In electric transformer furnaces,'the leakage fields around the primary coil as well as around the secondary conductor formed by the melting bath exert a considerable influent-e on the working conditions of the furnace, said fields attaining great values, on account of the con'i mratively great distance between the primary and secondary conductors, thus causing considerable tensions of self-indtution in each conductor.

The object of this invention is to suppress, to a considerable extent, the said leakage field, especially that around the primary coil.

The invention-consists, chiefly, in the ar' rangement in the leakage field of the furnace, of one or more conductors, said conductors forming closed electric circuits in in ductive relation to the said leakage fields but beingarranged, with relation to the main tield,--in such'a manner as not to be 4 cfiective'ly induced by the same. Preferably, the invention can be carried out by placing, around the field-core, a short-circuited con- -ductor having two coils placed at a distance from each other and wound in opposite directions, each coil consistin generally, of only one winding and connected in such a manner as not to be effectively induced by the main field, whereas the lines of force of the leakage field or fields pass through the closed circuit of the conductor and excite therein a current counteracting the said field. Such short-circuitcd conductors may suitably 'be termed leakage-field-coils.

In the accom ninying drawing some forms of embodiment of my invention are schemat ically illiistrated.

.one form of the invention. Fig. 2 shows a plan-view of the short-circuit conductor employed therein. Figs. 5-) and 4show-twosections, at. right angles to each other, of a seethat in the part 7.

Figure 1 shows a vertical section through 0nd form of the invention. Fig. 5 shows a vertical section through a third form of the invention. Fig. (3 shows a plan-view of the short-circuit conductor employed according to Fig.

The furnace shown in Fig. ,1 is provided, as usual, with an'annular' melting space 2 arranged in a suitable brickwork l as well with a primary coil 3 placed around the shank of the closed iron core 4 passing through the central opening in the brickwork. In such an arrangement of the primary and secondary conductors of the furnace, leakage-fields are created about the said conductors, the limits of the said leakage-fields in the right half-part of the sections shown being represented by the dotted lines 5, 6 respectively. The direction of the flux of the lines of force in a given moment are supposed to be those indicated by the arrows. Now, in order". to neutralize 1 the leakage-field from the primary coil, there is placed, beneath the primary coil, a short circuited conductor or-'loop consisting of a central part 7, situated immediately below the primary coil 3, and an outer part 8 whose diameter is so large that it. substantially incloses the leakage field of the primary coil and which is so arranged that the current in the same will run in opposite direction to As easily understood, the main field in the closed iron core exerts the same inducing action in the parts 7 and S of the short-circuit loop or conductor 7. 8, and inasmuch as these parts are connected in series so that the induced currents will flow in opposite directions, the result of this induction will be zero. The leakagetield of the primary coil flowing between the parts 7 and 8 excites in the short-circuit conductor a current. counteracting the leakage-field.

As indicated in the drawing, also a part of the leakage-field of thejsecondary conductor passes through the space between the hoops 7 and 8 formed by the short-circuit conductor, and, inasmuch as this field has the same direction the primary one, also this leakage-field is partly counteracted by the current produced in the short-circuit conductor. As easily seen,'the possibility of counteracting the leakage-field of the secondary conductor is to an essential degree dependent upon the possibility of placing the short-circuit. conductor in close proximity to the secondary conductor. As the secondary conductor can here be formed by a thick cable or bar without electric insula- 'tion, it is easily understood that the said conductor can without danger be allowed to be heated to a high temperature, so that it can be placed, without any very great danger, close up to or within the brickwork at an inconsiderable distance from the melting bath. It is also obvious that more than one short-circuit conductor of the kind denishes an effective means of suppressing, to

an essential degree, the injurious consequences of disposing the primary coil outside the part of the lron core inclosed by the secondary conductors, for instance on any of the horizontal shanks of the iron core, in that by placing one winding ofa conductor or loop close around or within the primary coil and connecting this winding with a winding around the central iron core, as

shown in Figs. 3 and 4, the leakage-field s.

may be employed for producing in these windings a current tending to blow away the leakage-fields. ,Such an arrangement is schematically shown in Figs. 3 and 4. The primary coil 3 is placed around the upper 1 horizontal shank of the iron core 4. As

easily understood, a strong leakage-field will be created about the primary coil which, in case no measures were taken to prevent it, would entail unfavorable working conditions for the furnace. According to this invention, a short-circuit conductor in two sections is arranged about the iron core. The current produced therein has no action upon the main field passing through the iron core,

the direction of current in one part being opposite .to that in the other part in relation to the iron core. The parts of the primary and secondary leakage penetrating the space between 7 and '8 produces a current in the short-circuit conductor, which current tends, 1n the same manner as in the arrangement shown 1n Flgs. 1 and 2, to counteract 0 Fig. 5 shows a short-circuit conductor acting to suppress the chief parts of the primary as well as of the secondary leakagefield. This effect is gained by extending the inner part of the short-circuitconductor along the wholg primary coil and placing its outer part as near the melting bath as possible. For the rest, the arrangement is analogous to that illustrated in Figs. 1 and 2 in that the two parts 7 and 8 are connected to each other in such a manner that'their windings run in opposite directions. The advantage of this arrangementis especially obvious, when the furnace is built with a melting bath of a great diameter;

In order to obtain the greatest possible effect it is advantageous to divide the primary coil, or the short-circuit conductor, respectively, into parts arranged between one another. In certain cases the leakagefield-coilcan be built up of solid copper plates. For instance, in Fig. 2, it might consist of a circular diskhaving at the middle tl'iereof a circular opening for the central iron core and being also cut radially.

Having nowdescribed my invention, what I claim as new and desire to secure by Letters Patentis: I

1. The combination with an electric transformer furnace having a magnetic core, of

a main coil therefor, and a conductor comprising t'wo short-circuited wlndings lnclosing the magnetic core and extending around the same in opposite directions for reducing the eflect of the magnetic leakage in. said magnetic coil and said main coil.

2. In an electric transformer furnace, the combination of an annular melting bath, a closed iron core having *one' shank inclosed by the said melting bath, aprimary coil surrounding part of said iron core, said coil being so placed as to surrounda part of said iron core not inclosed by the melting bath, and arranged on the shank which ex tends at a right angle to the perpendicular of the shank inclosed by said melting bath, and a short-circuit conductor having two windings for blowing away magnetic leakage of said iron core and said coil, one of which is placed in immediate proximity to the primary coil and adapted to surround the same, while the other is arranged to surround the shank inclosed by the. melting bath. 7 i

3. The combination with an electric transformer furnace, having a main field and a leakage field, of a conductor formed with windings'arranged in inductive relation to the leakage field and main field so that the combined inductive efi'ects upon the conductor due to the main field and leakage field will be zero.

- In testimony whereof I havesigned my name to th1s specificationln the presence of two subscriblng wltnesses. 1

OTTO. FRICK.

Vvitnesses AUG. SonENsEN,

:KARB Runosnoe. 

